1. Field of the Invention
The present invention relates generally to a heat dissipation unit and a thermal module thereof. The heat dissipation unit includes a metal main body having a chamber. An oxide coating is deposited on wall surface of the chamber instead of capillary structure. The oxide coating serves to enhance vapor/liquid circulation efficiency of the working fluid in the chamber of the heat dissipation unit so as to increase heat dissipation efficiency.
2. Description of the Related Art
It is known that in operation, the electronic components of an electronic device generate heat at the same time. Most of the heat is generated by operation chips in operation. Following the more and more increased operation performance of the chips, the power of the chips has been up to 100 watts. The heat must be dissipated by means of a heat dissipation unit at high efficiency. Otherwise, the temperature of the chips may rise to over 100° C.
Most of the current chips are made of semiconductor such as silicon. The chip has numerous metal leads and insulation films inside. The expansion coefficients of these two materials are several times different from each other. As a result, when the chip repeatedly operates at a temperature over 90° C., the chip often eventually cracks and damages.
In order to avoid burnout of the chip due to overheating, the waste heat generated by the current must be dissipated in time. Therefore, the chip is often in contact with a copper plate or embedded in a metal-based ceramic sintered body such as aluminum-based silicon carbide, which currently has highest heat dissipation efficiency, for dissipating the heat. In addition, a heat dissipation unit is provided to help in increasing the heat dissipation efficiency so as to avoid burnout of the chip due to too high temperature. The heat dissipation unit is generally a radiating fin assembly, a heat sink or a heat pipe. Moreover, a cooling fan is usually provided to carry away the heat by forced convection so as to dissipate the heat and lower the temperature.
There is a trend to thin the electronic device. To catch up this trend, the heat dissipation unit used in the electronic device must be thinned in accordance with the requirement of miniaturization. However, while reducing the thickness of the heat dissipation unit, the internal passage for the vapor and space for the capillary structure of the heat dissipation unit must be preserved. This makes it quite difficult to achieve the object of miniaturization of the heat dissipation unit.
Furthermore, sintered powder body and mesh body are currently most popularly used in the heat pipe as the capillary structure. Such structure has some shortcomings. For example, after thinned, the internal vapor chamber of the heat pipe is completely narrowed. This deteriorates the flowability of the vapor and affects vapor/liquid circulation of the working fluid. As a result, the heat dissipation unit will have lowered heat dissipation efficiency or even fail.
Also, when manufacturing the heat dissipation unit by means of pressing, the internal capillary structure is subject to damage to lead to a defective product.
According to the above, the conventional heat dissipation unit has the following shortcomings:
1. The vapor/liquid working fluid has poor flowability.
2. It is difficult to process the conventional heat dissipation unit.
3. The ratio of defective products is higher.